CN1529538A - Organic Electroluminescent Devices - Google Patents

Abstract

An organic electroluminescent device comprising an organic layer with a light-emitting region is characterized in that the organic layer includes at least one distyryl compound of general formulas (4)-1 to (4)-10.

Description

Organic Electroluminescent Devices

The present invention relates to an organic electroluminescent device (organic EL device), wherein an organic layer having a light emitting region is arranged between an anode and a cathode.

Lightweight and highly efficient flat panel displays have been extensively researched and developed for use as picture tubes in computers and televisions, for example.

Due to its high luminous intensity and good color reproducibility, the Braun tube (cathode ray tube CRT) is currently widely used for display. However, various problems still exist, such as bulky tube body and high power consumption.

As high-efficiency light-weight flat panel displays, liquid crystal displays of an active matrix drive type have been introduced on the market. However, liquid crystal displays have problems in that they have a narrow field of view, do not rely on self-illumination, require large power consumption for backlighting when placed in a dark environment, and lack sufficient response to high-precision high-speed video signals that may be used in the future. . In particular, there is difficulty in manufacturing a liquid crystal display with a large image size, and at the same time, there is a problem in high manufacturing cost.

A type of display using light-emitting diodes can be used as an alternative, but this display is also expensive to manufacture and has other problems, such as difficulty in forming a matrix structure of light-emitting diodes on a substrate. Thus, when considered as a low-cost display option for use in place of cathode ray tubes, there are a number of issues that must be resolved before this type of display can become practical.

As a flat panel display that has the potential to solve these problems, an organic electroluminescence device (organic EL device) using an organic light-emitting material has recently been attracting attention. More specifically, by using organic compounds as light-emitting materials, flat panel displays using self-luminescence, which have a high response speed and are independent of the viewing angle, have been realized.

The organic electroluminescence device is configured such that an organic thin film containing a light-emitting material capable of emitting light by electric charges of an electric current is formed between a light-transmitting anode and a metal cathode. In a research report published in "Applied Physics Letters", Vol.51, No.12, pp.913-915 (1987), C.W.Tang and S.A.VanSlyke proposed a device structure (with a single organic EL device having a material structure), which has a two-layer structure including, as an organic thin film, a film composed of a hole transport material and a film composed of an electron transport material. In this device, light is emitted by the recombination of holes and electrons injected into the organic film from the respective electrodes.

In this device structure, both hole-transporting materials and electron-transporting materials are used as light-emitting materials. Luminescence is generated in a wavelength band corresponding to the energy gap between the ground state and the excited state of the luminescent material. When such a double-layer structure is used, the driving voltage can be significantly reduced while improving luminous efficiency.

Since then, someone has developed a three-layer structure (organic EL device with double heterostructure) consisting of hole transport material, light emitting material and electron transport material, see C.Adachi, S.Tokita, T.Tsutsui and S. Saito's research report was published in "Japanese Journal of Applied Physics", Vol.27, No.2, pp.L269-L271 (1988). In addition, the research report of C.W.Tang, S.A.VanSlyke and C.H.Chen published in "Journal of Applied Physics", Vol.65, No.9, pp.3610-3616 (1989) proposed a method including the existence Device structure of luminescent materials in electron transport materials. Through these studies, the possibility of emitting strong light at a low voltage has been confirmed, thereby giving rise to extremely extensive research and development recently.

Organic compounds used as light-emitting materials are considered to be advantageous because they are various in variety, and the color of light emission can theoretically be changed arbitrarily by changing their molecular structure. Therefore, three colors of R (red), G (green) and B (blue) with good color purity necessary for full-color display can be easily provided by appropriate molecular design compared with thin film EL devices using inorganic materials.

However, organic electroluminescent devices still have problems to be solved. More specifically, there are difficulties in developing stable red light-emitting devices with high luminance. DCM[ ₄ -dicyanomethylene-6-(p-dimethylaminostyryl )-2-methyl-4H-pyran] to obtain red light, this material is not sufficient as a display material in terms of maximum luminescence and reliability.

The BSB-BCN reported by T. Tsutsui and DU Kim at the Conference on Organic and Inorganic Electroluminescence (Berlin, 1996) can achieve high luminance above 1000 cd/m ² , but in terms of the chromaticity of red used as a full-color display Not always good.

The problem to be solved at present is how to realize a red light-emitting device with high brightness, stability and high color purity.

In Japanese Unexamined Patent Publication Hei 7-188649 (Japanese Patent Hei 6-148798), it has been proposed to use a specific type of distyryl compound as an organic electroluminescence material. However, the expected emission color is blue, not red.

Therefore, there is a need to develop an organic electroluminescent device capable of ensuring high brightness and stable red light emission.

In order to solve the above problems, sufficient research has been conducted, and it was found that when a specific type of distyryl compound is used as a light-emitting material, a high-reliability red light-emitting device can be provided, which is advantageous for realizing Stable full-color display with high brightness completes the present invention.

More specifically, the present invention relates to an organic electroluminescent device comprising an organic layer having a light-emitting region, disposed between a cathode and an anode, and containing, as an essential component, a An organic material characterized in that the organic layer includes at least one distyryl compound represented by the following general formula (1) or general formula (3) as an organic light-emitting material:

General formula (1):

In the above general formula (1), R ¹ , R ² , R ³ , and R ⁴ may be the same or different, and represent phenyl or aryl groups of the following general formula (2):

General formula (2):

In the above general formula (2), R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ may be the same or different, and each represent a hydrogen atom, or at least one of them is a saturated or unsaturated alkoxy group or an alkyl group (preferably methyl or tert-butyl), and R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R ¹² represent the same or different groups, and at least one of them represents cyano, nitro or halogen atoms (including F, Cl, Br or I),

General formula (3):

In the above general formula (3), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ and R ²⁵ respectively represent the same or different groups, and at least one of the groups represents a cyano group , nitro or halogen atoms (including F, Cl, Br or I).

As a kind of luminescent material, using the distyryl compound of the above general formula (1) and/or (3) can not only obtain stable red light emission with high brightness, but also can be made into a device with good electrical, thermal and chemical stability . The distyryl compounds of the general formula (1) or (3) can be used alone or in combination.

The distyryl compound used in the organic electroluminescent device of the present invention will be described below.

The distyryl compound represented by the general formula (1) and used as the luminescent material of the organic electroluminescent device of the present invention, for example, may have at least one of the following general structural formulas, the general formula (4)-1, (4 )-2, (4)-3, (4)-4, (4)-5, (4)-6, (4)-7, (4)-8, (4)-9 and (4)- 10. These are all bis(aminostyryl)naphthyl compounds having an alkoxy (or alkyl)phenyl group or an unsubstituted phenyl group.

Structural formula (4)-1:

Structural formula (4)-2:

Structural formula (4)-3:

Structural formula (4)-4:

Structural formula (4)-5:

Structural formula (4)-6:

Structural formula (4)-7:

Structural formula (4)-8:

Structural formula (4)-9:

Structural formula (4)-10:

Other objects and advantages of the present invention will become apparent by reading the following detailed description and appended claims, with reference to the accompanying drawings.

Fig. 1 is a schematic sectional view of the main part of the organic electroluminescent device of the present invention.

Fig. 2 is a schematic sectional view of the main part of another type of organic electroluminescence device of the present invention.

Fig. 3 is a schematic sectional view of the main part of another type of organic electroluminescent device of the present invention.

Fig. 4 is a schematic sectional view of a main part of still another type of organic electroluminescence device of the present invention.

Fig. 5 is a schematic structural view of a full-color flat panel display using the organic electroluminescence device of the present invention.

Fig. 6 is an emission spectrum diagram of the organic electroluminescent device in Example 1 of the present invention.

Fig. 7 is an emission spectrum diagram of the organic electroluminescent device in Example 2 of the present invention.

Fig. 8 is an emission spectrum diagram of the organic electroluminescent device in Example 5 of the present invention.

Fig. 9 is an emission spectrum diagram of the organic electroluminescent device in Example 6 of the present invention.

Fig. 10 is a graph showing the voltage-brightness characteristic curve of the organic electroluminescence device in Example 1 of the present invention.

Fig. 11 is a graph showing the voltage-brightness characteristic curve of the organic electroluminescent device in Example 2 of the present invention.

Fig. 12 is a graph showing the voltage-brightness characteristic curve of the organic electroluminescent device in Example 5 of the present invention.

Fig. 13 is a graph showing the voltage-brightness characteristic curve of the organic electroluminescent device in Example 6 of the present invention.

It should be understood that the drawings are not necessarily drawn to scale and that embodiments are sometimes illustrated by diagrams, dashed lines, diagrams, and details. In certain instances, portions of material which are not necessary to an understanding of the invention or which obscure other details may have been omitted. Of course, it should also be understood that the present invention is not limited to the specific solutions set forth herein.

1 to 4 each show an embodiment of an organic electroluminescent device according to the invention.

FIG. 1 shows a transmissive organic electroluminescent device A, wherein the light emission 20 passes through the cathode 3 , and the light emission 20 can also be observed from the side of the protective layer 4 . FIG. 2 shows a reflective organic electroluminescent device B in which the light reflected at the cathode 3 can also be obtained as luminescence 20 .

In the figure, reference numeral 1 denotes a substrate for forming an organic electroluminescent device, which can be made of glass, plastic and other suitable materials. When the organic electroluminescent device is used in combination with other types of display devices, the substrate 1 can be used in common. Reference numeral 2 denotes a transparent electrode (anode), for which ITO (Indium Tin Oxide), SnO ₂ or the like can be used.

Reference numeral 5 denotes an organic light-emitting layer containing the above-mentioned distyryl compound as a light-emitting material. For the layer configuration to obtain the organic electroluminescence 20, the light emitting layer may have hitherto known various types of layer configurations. As described below, if the material used for the hole transport layer or the electron transport layer has light emitting properties, for example, a combined structure of these thin films can be used. And, in order to improve the charge transport property within the scope of satisfying the object of the present invention, the hole transport layer or the electron transport layer or both may have a combination structure of thin films made of various types of materials, or may use a combination of films of various types of materials. The thin film composed of the mixture is not limited thereto. Furthermore, in order to improve light emission characteristics, at least one fluorescent material may be used to provide a structure in which a thin film of fluorescent material is sandwiched between a hole transport layer and an electron transport layer. Additionally, other types of structures may be used in which at least one fluorescent material is present in the hole transport layer or the electron transport layer, or both. In these cases, in order to improve luminous efficiency, a thin film for controlling hole or electron transport may be introduced in the layer configuration.

The distyryl compound represented by the structural formula (4) has electron-transporting properties and hole-transporting properties, and can be used as a light-emitting layer that also functions as an electron-transporting layer in a device configuration, or as a layer that also functions as a hole-transporting layer the luminous layer. In addition, a configuration in which the distyryl compound forms a light-emitting layer sandwiched between an electron-transporting layer and a hole-transporting layer can also be provided.

In FIGS. 1 and 2, it may be noted that reference numeral 3 denotes a cathode, and the electrode material may be made of active metals such as Li, Mg, Ca, etc. and alloys of metals such as Ag, Al, In, etc. In addition, a combined structure of thin films of these metals may also be employed. In transmissive organic electroluminescent devices, the light transmission required for the intended application can be obtained by controlling the thickness of the cathode. In the drawings, reference numeral 4 denotes a sealing/protecting layer, the effect of which is increased when the organic electroluminescence device is entirely covered therewith. Suitable materials can be used for this as long as airtightness can be ensured. Reference numeral 8 denotes a drive power supply for applying current.

In the organic electroluminescent device of the present invention, the organic layer may have an organic composite structure (single heterostructure) in which a hole transport layer and an electron transport layer are provided, and wherein the above-mentioned distyryl compound is used to form The material of the hole transport layer or the electron transport layer. In addition, the organic layer may also have an organic composite structure (double heterostructure) in which a hole transport layer, a light-emitting layer, and an electron transport layer are sequentially formed, and the light-emitting layer is formed of the above-mentioned distyryl compound.

The present invention shows an organic electroluminescent device with such an organic combined structure. More specifically, Figure 3 shows an organic electroluminescent device C having a single heterostructure composed of a combined structure, on a light-transmitting substrate 1, comprising light-transmitting anodes 2 sequentially stacked in the following order , an organic layer 5 a consisting of a hole-transport layer 6 and an electron-transport layer 7 , and a cathode 3 , the combined layer structure is sealed with a protective layer 4 .

With the layer configuration as shown in FIG. 3 (in which the light-emitting layer is omitted), light emission 20 having a given wavelength is emitted from the interface between the hole transport layer 6 and the electron transport layer 7 . This light is observed from the substrate 1 side.

Fig. 4 shows an organic electroluminescent device D having a double heterostructure composed of a combined structure, on a light-transmitting substrate 1, the combined structure includes light-transmitting anodes 2 sequentially stacked in the following order, transported by holes Layer 10 , the organic layer 5b composed of the light emitting layer 11 and the electron transport layer 12 , and the cathode 3 . The combined structure is sealed with a protective layer 4 .

In the organic electroluminescent device D shown in Figure 4, when a DC voltage is applied between the anode 2 and the cathode 3, the holes injected from the anode 2 reach the light-emitting layer 11 through the hole transport layer 10, and are injected from the cathode 3 The electrons also reach the light-emitting layer 11 via the electron-transport layer 12 . Finally, electron/hole recombination in the light-emitting layer generates singlet excitons, resulting in the generation of light with a given wavelength from the singlet excitons.

In the above organic electroluminescent devices C and D, the substrate 1 can be suitably made of a light-transmitting material, such as glass, plastic, and the like. When the device is used in combination with other types of display devices, or when the combined structure is arranged in a matrix as shown in FIGS. 3 and 4, the substrate can be commonly used. Both devices C and D can have a transmissive or reflective structure.

The anode 2 composed of transparent electrodes can use ITO (indium tin oxide), SnO ₂ and the like. In order to improve the charge injection efficiency, a thin film made of an organic material or an organometallic compound may be provided between the anode 2 and the hole transport layer 6 (or the hole transport layer 10 ). It should be noted that an insulating film may be provided on the anode 2 side when the protective layer 4 is formed of a conductive material such as metal.

The organic layer 5 a of the organic electroluminescent device C consists of a combined organic layer of the hole transport layer 6 and the electron transport layer 7 . The above-mentioned distyryl compound may be contained in one or both of these two layers, providing the light-emitting hole transport layer 6 or the electron transport layer 7 . The organic layer 5b of the organic electroluminescent device D is composed of a combined organic layer of a hole transport layer 10, a light emitting layer 11 comprising the above distyryl compound, and an electron transport layer 12. Layer 5b can adopt other types of combined structures. For example, one or both of the hole transport layer and the electron transport layer may have light emitting properties.

In particular, it is preferable that the hole transport layer 6 or the electron transport layer 7 and the light emitting layer 11 are each composed of a layer made of the distyryl compound used in the present invention. These layers may be formed of the above-mentioned distyryl compound alone, or by co-deposition of the above-mentioned distyryl compound and other types of hole or electron transport materials (eg, aromatic amines, pyrazolines, etc.). In addition, in order to improve the hole-transport property in the hole-transport layer, a hole-transport layer composed of a plurality of hole-transport materials that can be combined can be formed.

In the organic electroluminescent device C, the light emitting layer may be the electron transport light emitting layer 7 . At this time, light can be emitted from the hole transport layer 6 or the interface thereof according to the voltage applied from the power source 8 . Similarly, in the organic electroluminescent device D, the light-emitting layer can also be the electron-transport layer 12 or the hole-transport layer 10 in addition to the layer 11 . In order to improve light emitting performance, it is preferable to provide a structure in which the light emitting layer 11 containing at least one fluorescent material is interposed between the hole transport layer and the electron transport layer. In addition, the fluorescent material may be contained in the hole transport layer or the electron transport layer, or in both layers. In this regard, in order to improve luminous efficiency, a thin film for controlling hole transport or electron transport (hole blocking layer or exciton generating layer) may be provided in the layer configuration.

Materials used as the cathode 3 may be alloys of active metals such as Li, Mg, Ca, etc., and metals such as Ag, Al, In, etc. In addition, a combined structure of layers of these metals can also be used. Proper selection of cathode thickness and alloy type enables fabrication of organic electroluminescent devices suitable for their applications.

The protective layer 4 functions as a sealing film, and is configured to cover the organic electroluminescent device with its entirety, thereby ensuring improvement in charge injection efficiency and luminous efficiency. It should be noted that if airtightness is to be ensured, materials may be appropriately selected for this purpose, including single metals such as aluminum, gold, chromium, etc., and alloys thereof.

The current applied to each of the above-identified organic electroluminescent devices is usually direct current, but pulsed current or AC current may also be used. The requirements for the current value and voltage value are not strict, as long as they are within the range where the device is not broken down. Nevertheless, considering the power consumption and lifetime of organic electroluminescent devices, it is preferable to use as little electrical energy as possible to produce efficient light emission.

Next, FIG. 5 shows the configuration of a flat panel display in which the organic electroluminescent device of the present invention is used. As shown in the figure, for example, in the case of a full-color display, an organic layer 5 (5a, 5b) capable of producing red (R), green (G) and blue (B) primary color light emission is arranged between the cathode 3 and the anode 2 . The cathode 3 and the anode 2 can be arranged in the shape of intersecting strips, which are appropriately selected by the brightness signal circuit 14 and the control circuit 15 with a built-in shift register, and a signal voltage is applied to them. As a result, the organic layer at the intersection (pixel) of the selected cathode 3 and anode 2 emits light.

More specifically, FIG. 5 shows, for example, a simple matrix of 8×3RGB, wherein an assembly 5 composed of a hole transport layer, and at least one of an emissive layer and an electron transport layer is disposed between the cathode 3 and the anode 2 (see FIG. 3 or 4). The cathodes and anodes are laid out in stripes and cross each other in a matrix, and signal voltages are applied in time series from the control circuits 15 and 14 with built-in shift registers, thereby generating electroluminescence or light emission at the crossing positions. An EL device having such a configuration can be used not only for the display of letters/symbols but also for image reproduction equipment. In addition, the strip pattern of anode 3 and cathode 2 can be configured for each of red (R), green (G) and blue (B) colors, thereby making it possible to manufacture solid-state flat panel displays of multi-color or full-color type .

The present invention will be described more specifically by way of examples, but the present invention is not limited thereto.

Example 1

This example illustrates the use of the compound represented by the following structural formula (4)-1 as a hole transport luminescent material to prepare an organic electroluminescent device with a single heterostructure. The structural formula (4)-1 represents that R ² and R ³ represent respectively 3-Methoxyphenyl, R ⁴ and R ¹¹ respectively represent the distyryl compound of the general formula (1) of cyano group.

Structural formula (4)-1:

A 30mm×30mm glass substrate was placed in a vacuum deposition device, where one side of the substrate was a 100nm thick anode made of ITO. A metal mask having a number of 2.0 mm x 2.0 mm cell holes was placed next to the substrate as a deposition mask. The compound represented by the above structural formula (4)-1 is vacuum-deposited in a vacuum state of 10 ^-4 Pa or lower to form a hole transport layer (also serving as a light-emitting layer) as thick as 50 nm. The deposition rate was 0.1 nm/sec.

In addition, Alq ₃ [tris(8-quinolinolato)aluminum] represented by the following structural formula was provided as an electron transport material and deposited in contact with the hole transport layer. For example, the thickness of the electron transport layer made of Alq ₃ is set to 50 nm, and the deposition rate at this time is 0.2 nm/sec.

Alq ₃ :

A combined film of Mg and Ag is used as a cathode material. For this purpose, Mg and Ag are respectively deposited at a deposition rate of 1 nm/sec to form composite films such as 50 nm thick (Mg film) and 150 nm thick (Ag film). In this way, the organic electroluminescent device of Example 1 shown in FIG. 3 was produced.

By applying a positive bias DC voltage to the organic electroluminescent device fabricated in Example 1 in a nitrogen atmosphere, the luminescent properties of the device were evaluated. The luminous color is red, and then the device is subjected to spectral analysis, the result is shown in Figure 6, and the spectrum with a luminous peak at 680nm is obtained. Spectral analysis was performed using a spectrometer manufactured by Otuska Electronic Co. Ltd, while using a photodiode array as a detector. Furthermore, when a voltage-luminance measurement was performed on the device, a luminance of 3000 cd/m ² was obtained at a voltage of 8 volts, which has been particularly shown in FIG. 10 .

After the fabrication of the organic electroluminescence device was completed, the device was kept in a nitrogen atmosphere for one month, and no aging of the device was observed. Also, when the device was subjected to forced aging in which a certain value of current was maintained, continuous light emission was performed at an initial luminance of 300 cd/m ² , and as a result, 1500 hours elapsed before the luminance decreased to half.

Example 2

This example illustrates the preparation of an organic electroluminescent device with a single heterostructure using a compound represented by the following structural formula (4)-1 as an electron transport luminescent material. Structural formula (4)-1 represents wherein R ² and R ³ represent 3-methoxyphenyl respectively, R ⁷ and R ¹¹ represent cyano distyryl compounds of the general formula (1).

A 30mm×30mm glass substrate is placed in a vacuum deposition device, where one side of the substrate is a 100nm thick anode made of ITO. A metal mask having a number of 2.0 mm x 2.0 mm cell holes was placed next to the substrate as a deposition mask. In a vacuum state of 10 ^-4 Pa or lower, α-NPD (α-naphthylphenylenediamine) represented by the following structural formula is vacuum-deposited to form a hole transport layer having a thickness of eg 50 nm. The deposition rate was 0.1 nm/sec.

α-NPD:

In addition, the compound represented by the formula (4)-1 acts as an electron transport material and is deposited in contact with the hole transport layer. The thickness of the electron transport layer (which also serves as a light-emitting layer) composed of the compound represented by the structural formula (4)-1 is set to, for example, 50 nm, at which time the deposition rate is 0.2 nm/sec.

A combined film of Mg and Ag is used as a cathode material. At this time, Mg and Ag are respectively deposited at a deposition rate of 1 nm/sec to form a combined film of, for example, a thickness of 50 nm (Mg film) and a thickness of 150 nm (Ag film). In this way, the organic electroluminescent device of Example 2 as shown in FIG. 3 was produced.

The luminescent properties of the device were evaluated by applying a positive bias DC voltage to the organic electroluminescent device fabricated in Example 2 in a nitrogen atmosphere. The luminescent color is red, and then the device is subjected to spectral analysis as in Example 1, and the result is shown in Figure 7, and a spectrum with a luminous peak at 680nm is obtained. Furthermore, when the device was subjected to a voltage-luminance measurement, a ^luminance of 2500 cd/m2 was obtained at a voltage of 8 volts, which is particularly shown in FIG. 11 .

After the fabrication of the organic electroluminescent device was completed, the device was kept in a nitrogen atmosphere for one month, and no aging of the device was observed. Also, when the device was subjected to forced aging in which a constant value of current was maintained, continuous light emission was performed at an initial luminance of 300 cd/m ² , and as a result, 1000 hours elapsed before the luminance decreased to half.

Example 3:

This example illustrates the use of compounds represented by the following structural formula (4)-1 as light-emitting materials to prepare organic electroluminescent devices with a double heterostructure. The structural formula (4)-1 represents that R ² and R ³ represent 3-methano Oxyphenyl, R ⁷ and R ¹¹ respectively represent the distyryl compound of the general formula (1) of cyano group.

A 30mm×30mm glass substrate was placed in a vacuum deposition device, where one side of the substrate was a 100nm thick anode made of ITO. A metal mask having many 2.0 mm x 2.0 mm cell holes was placed near the substrate as a deposition mask. In a vacuum state of 10 ^-4 Pa or lower, the ?-NPD represented by the aforementioned structural formula is vacuum-deposited to form a hole-transporting layer with a thickness of, for example, 30 nm. The deposition rate was 0.2 nm/sec.

In addition, the compound represented by the aforementioned structural formula (4)-1 is used as a light-emitting material, and is deposited in contact with the hole transport layer. The thickness of the light-emitting layer composed of the compound represented by the structural formula (4)-1 is set to, for example, 30 nm, and the deposition rate at this time is 0.2 nm/sec.

Alq ₃ as an electron transport material is deposited in contact with the light-emitting layer. The thickness of the Alq ₃ layer was set at 30 nm and the deposition rate was 0.2 nm/sec.

A combined film of Mg and Ag is used as a cathode material. Mg and Ag are respectively deposited at a deposition rate of 1 nm/sec to form composite films such as 50 nm thick (Mg film) and 150 nm thick (Ag film). In this way, the organic electroluminescent device shown in Fig. 4 in Example 3 was produced.

The luminescent characteristics of the device were evaluated by applying a positive bias DC voltage to the organic electroluminescent device fabricated in Example 3 in a nitrogen atmosphere. The luminous color is red, and then the device is subjected to spectral analysis, and the spectrum with a luminous peak at 680nm is obtained as a result. In addition, when the voltage-luminance measurement was performed on the device, a luminance of 2500 cd/m ² was obtained at a voltage of 8 volts.

After the fabrication of the organic electroluminescent device was completed, the device was kept in a nitrogen atmosphere for one month, and no aging of the device was observed. Also, when the device was subjected to forced aging in which a certain value of current was maintained, continuous light emission was performed at an initial luminance of 300 cd/m ² , and as a result, 2200 hours elapsed before the luminance decreased to half.

Example 4

This example repeats the layer structure and film formation steps in Example 2, except that TPD (triphenyldiamine derivative) represented by the following structural formula is used instead of α-NPD as the hole transport material, thereby making an organic electroluminescent device .

The organic electroluminescent device of this example exhibits red light as in Example 2. Spectral analysis showed that the spectrum was consistent with that of the organic electroluminescent device in Example 2.

Example 5

This example illustrates the preparation of an organic electroluminescent device with a single heterostructure using a compound represented by the following structural formula (4)-6 as a hole-transporting light-emitting material. Structural formula (4)-6 represents the distyryl compound of general formula (3) wherein R ²⁰ and R ²⁴ respectively represent a cyano group.

Structural formula (4)-6:

A 30mm×30mm glass substrate was placed in a vacuum deposition device, where one side of the substrate was a 100nm thick anode made of ITO. A metal mask having many 2.0 mm x 2.0 mm cell holes was placed near the substrate as a deposition mask. The compound represented by the above structural formula (4)-6 is vacuum-deposited in a vacuum state of 10 ^-4 Pa or lower to form a hole transport layer (also serving as a light-emitting layer) as thick as 50 nm. The deposition rate was 0.1 nm/sec.

In addition, Alq ₃ [tris(8-quinolinolato)aluminum] represented by the aforementioned structural formula was provided as an electron transport material and deposited in contact with the hole transport layer. The thickness of the electron transport layer made of _Alq3 is set to be, for example, 50 nm, and the deposition rate at this time is 0.2 nm/sec.

A combined film of Mg and Ag is used as a cathode material. Mg and Ag are respectively deposited at a deposition rate of 1 nm/sec to form composite films such as 50 nm thick (Mg film) and 150 nm thick (Ag film). In this way, the organic electroluminescence device shown in Fig. 3 in Example 5 was fabricated.

The light-emitting characteristics of the device were evaluated by applying a positive bias DC voltage to the organic electroluminescent device fabricated in Example 5 in a nitrogen atmosphere. The luminescent color is red, and then the device is subjected to spectral analysis, and the spectrum with a luminous peak at 670nm is obtained as a result. Spectral measurement was performed using a spectrometer manufactured by Otuska Electronic Co. Ltd, while using a photodiode array as a detector. Furthermore, when voltage-luminance measurements were performed on the device, a luminance of 4000 cd/m ² was obtained at a voltage of 8 volts, as shown in FIG. 12 .

After the fabrication of the organic electroluminescent device was completed, the device was kept in a nitrogen atmosphere for one month, and no aging of the device was observed. Also, when the device was subjected to forced aging in which a certain value of current was maintained, continuous light emission was performed at an initial luminance of 300 cd/m ² , and as a result, 2000 hours elapsed before the luminance decreased to half.

Example 6

This example illustrates the preparation of an organic electroluminescent device with a single heterostructure using compounds represented by the following structural formulas (4)-6 as electron transport light emitting materials. The structural formula (4)-6 represents wherein R ²⁰ and R ²⁴ respectively represent the distyryl compound of the general formula (3) representing a cyano group.

A 30mm×30mm glass substrate was placed in a vacuum deposition device, where one side of the substrate was a 100nm thick anode made of ITO. A metal mask having a number of 2.0 mm x 2.0 mm cell holes was placed next to the substrate as a deposition mask. α-NPD (α-naphthylphenylenediamine) represented by the above-mentioned structural formula is vacuum-deposited in a vacuum state of 10 ⁻⁴ Pa or lower to form a hole transport layer of eg 50 nm thick. The deposition rate was 0.1 nm/sec.

In addition, the compound represented by the formula (4)-6 acts as an electron transport material and is deposited in contact with the hole transport layer. The thickness of the electron transport layer (also serving as the light-emitting layer) composed of the compound represented by the structural formula (4)-6 is set to be, for example, 50 nm, and the deposition rate at this time is 0.2 nm/sec.

A combined film of Mg and Ag is used as a cathode material. At this time, Mg and Ag are respectively deposited at a deposition rate of 1 nm/sec to form composite films such as 50 nm thick (Mg film) and 150 nm thick (Ag film). In this way, the organic electroluminescent device shown in Fig. 3 in Example 6 was fabricated.

The light-emitting characteristics of the device were evaluated by applying a positive bias DC voltage to the organic electroluminescent device fabricated in Example 6 in a nitrogen atmosphere. The luminous color is red, and then the device is subjected to spectral analysis as in Example 1, and the result is shown in Figure 9, and a spectrum with a luminous peak at 670nm is obtained. Furthermore, when the device was subjected to a voltage-luminance measurement, a ^luminance of 3500 cd/m2 was obtained at a voltage of 8 volts, which is particularly shown in FIG. 13 .

After the fabrication of the organic electroluminescent device was completed, the device was kept in a nitrogen atmosphere for one month, and no aging of the device was observed. Also, when the device was subjected to forced aging in which a certain value of current was maintained, continuous light emission was performed at an initial luminance of 300 cd/m ² , and as a result, 1500 hours elapsed before the luminance decreased to half.

Example 7

This example illustrates the preparation of an organic electroluminescent device with a double heterostructure using a compound represented by the following structural formula (4)-6 as a light-emitting material. Structural formula (4)-6 represents the distyryl compound of general formula (3) wherein R ²⁰ and R ²⁴ respectively represent a cyano group.

A 30mm×30mm glass substrate was placed in a vacuum deposition device, where one side of the substrate was a 100nm thick anode made of ITO. A metal mask having many 2.0 mm x 2.0 mm cell holes was placed near the substrate as a deposition mask. The α-NPD represented by the above-mentioned structural formula is vacuum-deposited in a vacuum state of 10 ^-4 Pa or lower to form a hole transport layer with a thickness of, for example, 30 nm. The deposition rate was 0.2 nm/sec.

In addition, the compound represented by the above-mentioned structural formula (4)-6 is used as a light-emitting material, and is deposited in contact with the hole transport layer. The thickness of the light-emitting layer composed of the compound represented by the structural formula (4)-6 is set to, for example, 30 nm, and the deposition rate at this time is 0.2 nm/sec.

Alq ₃ represented by the aforementioned structural formula acts as an electron transport material and is deposited in contact with the light-emitting layer. The thickness of Alq ₃ is set to be, for example, 30 nm, and the deposition rate at this time is 0.2 nm/sec.

A combined film of Mg and Ag is used as a cathode material. At this time, Mg and Ag are respectively deposited at a deposition rate of 1 nm/sec to form structural films such as 50 nm thick (Mg film) and 150 nm thick (Ag film). In this way, the organic electroluminescent device shown in Fig. 4 in Example 7 was fabricated.

The luminescent characteristics of the device were evaluated by applying a positive bias DC voltage to the organic electroluminescent device fabricated in Example 7 in a nitrogen atmosphere. The luminescent color is red, and then the device is subjected to spectral analysis, and the spectrum with a luminous peak at 670nm is obtained as a result. In addition, when the device was subjected to a voltage-luminance measurement, a luminance of 5000 cd/m ² was obtained at a voltage of 8 volts.

After the fabrication of the organic electroluminescent device was completed, the device was kept in a nitrogen atmosphere for one month, and no aging of the device was observed. Also, when the device was subjected to forced aging in which a constant value of current was maintained, continuous light emission was performed at an initial luminance of 300 cd/m ² , and as a result, 2400 hours elapsed before the luminance decreased to half.

Example 8

In this example, the layer structure and film formation steps in Example 6 were repeated except that TPD (triphenyldiamine derivative) was used instead of α-NPD as the hole transport material, thereby producing an organic electroluminescent device.

The organic electroluminescent device of this example exhibits red light as in Example 6. Spectral analysis results show that the spectrum is consistent with the spectrum of the organic electroluminescent device in Example 6.

According to the organic electroluminescent device of the present invention, wherein an organic layer having a light-emitting region is arranged between the anode and the cathode, the organic layer includes at least one distyryl compound represented by the general formula (1) or (3), thereby providing An organic electroluminescent device with high brightness and stable red emission has been obtained.

From the foregoing description it is apparent that the objects of the present invention have been achieved. While only a few specific embodiments have been listed, other embodiments and various modifications will be apparent to those skilled in the art from the foregoing description. These and other embodiments are considered equivalents and within the scope and spirit of the invention.

Claims (4)

1. organic electroluminescence device comprises:

Negative electrode and anode,

Have the luminous zone and be arranged on negative electrode and anode between organic layer, this organic layer contains at least a distyrene compound that following structural is represented that is selected from:

With

2. according to the organic electroluminescence device of claim 1, wherein said organic layer comprises hole transmission layer and electron transfer layer, wherein contains described distyrene compound in the hole transmission layer.

3. according to the organic electroluminescence device of claim 1, wherein said organic layer comprises hole transmission layer and electron transfer layer, wherein contains described distyrene compound in the electron transfer layer.

4. according to the organic electroluminescence device of claim 1, wherein said organic layer comprises hole transmission layer, and luminescent layer, and electron transfer layer wherein contain described distyrene compound in the luminescent layer.

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